Metal tube and method of making same



MayZS, 1929- I W. J. lawslimlsolv 1,715,099

METAL TUBE AND METHOD OF MAKING SAME Filed Nov. 2o. 1922 4 shets-sheet 1l 77x25 ivmey May 228, 1929. w. J. ROBINSON METAL TUBE AND METHOD OFMAKING SAME Filed NOV. 20. 1.922 4 Sheets-Shea?l 2 May 28, 19x29. W, J,ROBlNsON 1,715,099

METAL TUBE AND METHOD 0F MAKING SAME Filed Nov. 20. 1922 4 Sheets-Sheet3 May 28, 1929. Y w, J, RQ'BlNSON 1,715,099

METAL TUBE AND METHOD OF MAKING SAME Filed Nov. zo. 1922 '4 sheets-sheet4 named' May 2s, 1929.

UNITED sTATEs WILLIAM J. nonrNsoN,

MENTS, To wmcnnsrnn BEPEATING Amas company,

CUT, A CORPORATION F DELAWARE.

0F LOWELL, MASSACHUSETTS, ASSIGNOR, BY HESNE ASSIGN- or :mw mvaN,commeri- METAL TUBE AND :BETH-0D 0F MAKING' SAIE.

Application led November 20, 1922. Serial No. 802,289.

This invention relates to metal tubes and more particularly to thinmetal, usually coper tubes, for the radiators of automobiles,

and other heat exchangers, the `walls of such ,5 tubes having athickness of the order of fivethousandths of an inch.

Heretofore it has been customary to make radiator tubes and other thin'ltubes from sheet copper stock by stamping a disc from the stock and thenbending up the margin of the disc to form a cupped'blank which 1s thenannealed and thereafter extruded into the form of the tube by the singlestroke of an extruding plunger. I have found this method unsatisfactoryin many respects and I believe the followino' to be -a substantiallycorrect explanationoiP the reasons therefor.

In cupping a flat disc the center becomes the bottom of the cup and thesurrounding part becomes the side-wall or rim of the cup. The metal inthe latter part is condensed, whereas at the corner between the sidewall and bottom it is bent and therefore to some extent stretched. Thisbending produces incipient fractures which persist throughout subsequentoperations and is' so pronounced especially in cups intended for theextrusion of small diameter tubes as to` prohibit their manufacture on acommercial basis.

Thin tubes made from sheet stock as above described frequently havewrinkled walls and often display cracks in the walls. Moreover, suchtubes have a tendency to develop leaks or fractures in subsequentmanipulations. For example, in making radiator tubes it is desirable tohex the ends of the tubes for assembly into groups and also to indentthe walls to form air baies within the tubes. When usin tubes made fromsheet material as describe the hexing and indenting is not uniform andthe tubes are frequently dis-- torted and cracked in these operations.Also the making of the cups involves a considerable waste of metalbecause the pieces of metal in- 45. tervening between the round discs inthe flat sheet are necessarily lost as waste.

In making tubes from cast blanks there are. dificulties due, I believe,to the fact that the blanks do not consist of homogeneous metal nor ofequal amounts of metal and therefore are not well suited to flowuniformly under` extrusion by impact pressure.

Theprincipal obj ects of the present invention are to overcome theaforesaid disadvantages and diflculties, to make tubes by hammer-strokeextrusion which are stronger and morel uniform, to extrude tubes moreeconomically both with respect to the elimination of Wastage and thewear on the dies, to extrude the metal into tube form without need ofheatin the metal and so as to make thin walled tues, especially tubesabout a quarter inch diameter and about nine inches long, which aresubstantially free v:from internal stresses, which will not wrinkle, andwhich will not readily crack when indented or otherwise shaped forradiator orother uses.

My improved method involves the cutting of a rod into sections to formcylindrical blanks, having substantially parallel grain throughout andcausing the metal to flow by impact extrusion in a direction which 1sparallel to the axis and grain of the blank, into the form of a tube.The lmetal is extruded cold, that is without preheating. The cylindricalform and parallel arrangement of the grain of the blank is secured byusin a section of a rod which is formed preferably by an extrusionprocess or other process adapted to produce lines of flow vapproximatelyparallel to each other and to the axis of the rod. lThe rod from whichthe blanks are cut is circular in section and may be a tubular rod, inwhich case the rod sections may be extruded without any preliminary shaing. However, if the rod is a solid rod, tge rod sections are preferablyprovided with axial openings before being extruded. The axial openingsmay extend entirely through the blanks so as to form hollow cylindricalblanks or rod sections or they may be in the form of indentationsextending only part way through so as to form hollow cup-shaped blanksor rod sections. When vthese openings are formed by punches they arepreferably produced in two stages, the first stage producing an axialdent in one end of the blank and the second stage extending the openingeither wholly or substantially through the blank. The outer lsurfaces ofthe blanks are kept smooth and true in these indenting operations, byconflning the blanks in dies of suitable diameter while being punched.

If the blanks are formed with axial openings extending entirelytherethrough, the resultant tubes are open at both ends which ispreferred. If the axial openings extend only part way through theblanks, tubes open at both ends may bottom of the culpped blank by theformer of the extruding p unger in the initial state of the extrusion oeration. v

In an case I ave ascertained that the rod from w ich the blank is cutmust be homo.

geneous in respect to its crystalline structure and in respect to thedistribution vthrough the metal of such impurities as may be present.Any rod stock is suitable which complies with these requirements. Anyextruded rod is generally found to do s o, because such rod is producedfrom a large sized lngot, generall quite pure. Rolled stock is apt tobe.4

nonomogeneous if it is rolled from an ingot that was poured in ahorizontal mould, because in such case the impuritles tend to `riseduring the cooling so as to occupy the upper part of the in ot after ithas set. When such an ingot is ro led into rod, the lmpurlties thereinwillbe found more on one side than the other, but the use of rolled rod'stock is nevertheless satisfactory and within the 1nvention and can beproduced of sufficiently homogeneous condition to avoid much of thewaste that has heretofore been incident to the impact extrusion of tubesfrom sheet stock.

My improved method results in tubes whose metallurgical structure isstrong and smooth, whose walls are of uniform thickness, and which areadapted to be indented or otherwise Shaped without fracturing. Thecrinkled condition found in prior tubes, indieating strained andover-worked metal, is entire] to be ue to the use of blanks cut from rodstock, and in some measure to the use of a blank having substantiallyparallel grain throughout and to the working of the metal longitudinallyof the axis of the blank in each stage of the process.

According to the present invention, in-

i volving the use of rod stock, there is praci for cutting the rodstieally no Waste material, each rod-section blank beingsubstantiallywholly converted into tubular form. This is a markedadvantage over the prior methods using sheet stock where about one-thirdof the stock is Wasted in stamping out the disc blanks.

IIn order more clearly to set forth the invention certain concreteexamples have been illustrated in the accompanying drawings, in which Fi1-is a diagrammatic view of one method o making rods for use according`to the present invention;

Fig. 2 is a sectional view of the machine into sections;

Fig. 3 is a perspective View of a rod section;

Fig. 4 is a diagrammatic illustration of one step 1n forming the blank;

Fig. 5 is a sectional view of the blank as shaped in the step shown inFig. 4;

be formed by puncturing the absent. These advantages I believev Fig.' 6is a diagrammatic illustration of the next step in forming the blank;

Fig. 7 is a sectional view. of the blank after the forming step shown`in Fig. 6;

' Fi 8 shows another method of forming the rod or use according to thepresent invention, this rod being tubular;

Fig. 9 is a section of the rod formed as illustrated in Fi 8; l

Fig. 10 is a dlagrammatic illustration of the extrusion of the blankinto the form of a tube; i

Fig. 11 is a similar view stage of the process;

lFig. 12 is an elevation of, the resulting tu e;

Figs. 13 and 14 are perspective views of dies for indenting walls of thetube for radi`- ator purposes;

Fig. 15 is a developm-cnt'of the operative faces of the dies, showingthe distribution of the indenting elements;

Fig. 16 illustrates, matically, the method of simultaneously hexing theends of the tube and indenting gig. 17 is a side view of the finishedtube; an

Fig. 18 is an ond radiator tube.

In Fig. 1, I have shown, more or less dia# grammatically a common Way offorming copper rod, namely by forcing a mass of pure copper M softenedby heat through a restricted round opening into the form of a rod R, Drepresenting the die through which the metal is forced, and P theplunger which is hydraulically'operated. The rod R is cut olf in lengthsand passed through sizing or straightening rolls and is then ready to becut up into sections to form blanks.

Fig. 2 illustrates suitable means for cutting the rod R into sections,rapidly and uniof a succeeding elevation of the finished formly andwithout deforming the structure r of the rod. This machine comprises a`bed plate 1, a vertically reciprocating head 2 and the cam roll 5against the cam 4. The head 2 also carries a plunger 7 adapted to forcethe rod sections from the machine after being severed. The rod R is feddownwardly through an opening 8 into the opening of an annular die 9carried by the slide 3. As the slide is forced to the left by the cam 4,a section of the rod is severed along the dotted line 10 and is thencarried into alignment with the opening 11 and the plunger 7. Uponfurther descent of the head 2, the plunger 7 forces the rod section Yfrom, the die 6 through the opening 12. The rolling of the rod in theprocess of manufacture produces a slightlyhardened surface thereon whichtruding plunger,

grammatically, ways of forming the axialV opening in the rod section. InFig. 4 D1 represents a die, P1 a plunger, and A a bottom or ejectorplunger. -The severed rod section, after bein first annealed,I -isplaced in the die D1 wit the plun er A held in the position indicated,and t e plunger l?1 is thenf' forced down into the rod section until therod section is formed substantially into the shape indicated at C inFigs. 4 and 5, the plunger P1 is then withdrawn and the plunger Aadvanced to remove the 4blank from the die. The blank is then placedafter another annealing, `in die D2, Fig. 6, with the plunger A2 in theIposition indicated, whereupon the lunger 2 is advanced until the blankis ormed into substantially the shape indicated at B in Figs. 6 and 7.The plunger P2 is then withdrawn and the plunger A2 advanced to re#move the blank from the die.

In each of the operations illustrated in Figs. 4 and 6, the ow of metalis along the axis of the rod blank, the surrounding dies restraining themetal against later al flow as the plun ers advance. axially into theblanks, and the isplacement of the metal is equal in every radialdirection, so that the metal in the resulting blank is' of uniformcondition on all sides of its longitudinal axis.

In the operation shown in Fig. 6, the formingplunger may pass eitherentirely through the lunger so as to leave a small axial opening inthebase of the cup'Bl or it may be ad' vancedonlyto, the point where thebase of the cup B is very thin as shown in Fig. 7.

Fig. 8 illustrates, more or less diagrammatically, the method ofextruding a hollow rod section, or blank, in which the grain islongitu'dinal of the rod. In this figure, Da represents an extrudin die,Is the hydraulic ex- 2 a mass of hot copper and B the resultlng tubularrod. Fig. 9 represents a section of this blank on a larger scale.

Fig. 10 illustrates the operation of extruding ythe blank into the formof a thin tube ladapted for radiator purposes or other uses. Inthisfigure, D* represents the die, P* the extruding lunger, and T theresultinv tube. With the p unger P4 retracted the blark (for exampleth'e blank B of Fig. 7 or the blank B of F ig'. 9) isl placed in the dieD4 and the plunger P4 is caused to strike it a sharp blow which squirtsor extrudes the metal through the restricted annular orifice formedbetween the lip at the bottom of the die cavity and the reduced diameterextension, or former, on the end of the plunger P". This orifice givesthe shape to the tube which then projects or hangs therefrom by theunextruded portion, or flange, still remaining 'in the die cavity. Itwill be understood that the extrusion is done the metal in a cold orAnormal temperature and that the blank is flooded with oil at u `themoment of plunger impact. Thefextru sion operation may be carried on inany suitable apparatus, such for exampleas that shown in Hooker PatentNo. 918,154 and such apparatus is commonly used in an-ordinary cranktype press running at a speed of about 120 operations a minute, ascustomary for the Yimpact extrusion process. The blank, when ready forintroduction into the extrusion die is shaped to fit the same snuglyAand the indentationtherein is carefully made so as to be central of theblank and to fit the former on the extruding plunger. Preferably thecopper in the blankis of the grade known as electrolytic, althou h theprocess is applicable to any metal which offers substantially the' sameresistance to cold extrusion as coppor and copper alloys. If it isdesired to' make an open end tube from ac'losed bottom cup blank such asshown in Fig. plunger P4 may be pointed to puncture the base of theblank before extrusion begins.

After the plunger' P2 has made its stroke into the position shown inFig. 10, it is retracted and a trimming plunger such as shown at P5 inFig. 11, is advanced into the die D2. The plunger P5 hasV an annularshoulder, G which severs the flanged upper end of the-tube to trim andrelease the tube T, the severed angebeing carried out of the die by theshoulder G as the plunger P5 is retraeted. f i

The resulting tube T shown in Fig. 12 is extremely thin and at the sametime stron g and uniform. In the case of radiatpr -tubesfor example, thetubes are commonly .268 inches in diameter and 4have a wall thickness of.006 inch. Such tubes can not be commercially .produced from sheet stockby cold impact extrusion as far as I am aware. For the purposes ofillustration it has been necessary to show the walls of the tubesdisproportionately thick. They are commonly about nine and a half`inches long and for automobile radiators they are then cut in two ormore sections.

The indenting dies D5 and Dl shown in Figs. 13 and 14 have opposingsemi-cylindrical recesses in which are provided indenting die el'ementsa, b, c and d, these die elements being distributed both axially andcircumferentially of the recesses. FigaV 15 shows an effectivedistribution of these dieelements, it

7, the forward end of being understood that the indentations pro-v thetube, the semi-cylindrical recesses engag- A ing the tube on all sldesof each die element to prevent the tube from being-distorted orcollapsed. After the die elements have been rfully advanced, so thatthey entirely surround the tube, end formin plungers P". and Pfareadvanced Vinto the en s of the tubes, the plungers havin hexagonal endsadapted to cooperate w1th hexagonal dies Bland D8 to hex the ends of thetubes. Inv this operation die elements a, b, c and d, which are intrudedinto the Walls of the tube, hold the tube against longitudinal movement,thereby insuring that the tube is hexed the salne axial distance at bothends. l

Figs. 17 and 18 illustrate the resulting tube T having nthe hexed ends Hand the baffle indentations a', b', o anda?. By forming the tubes asherein described, these indentations can be formed uniformly and Withoutcracking or deforming the tubes.`

yof a hollow rod, cutting olf a section of the rod to form a hollowcylindrical blank, and extruding the unheated metal longitudinally ofthe blank intothe form of a thin t'ube.

3. The method of making metal tubes which comprises forming a rod bycausing a body of metal when cold to flow longitudinally of the axis ofthe rod, cutting a section from the rod to form a blank, and causing theunheated metal of the blank to flow longitudinally of said axis into theform ofa tube.

4.. The method of making radiator tubes which comprises flowing metalinto the form of a tube from a. blank having substantially parallelgrain throughout, the flow being lon-v gitudinal of the grain of theblank, and inp denting the tube transversely of the grain.

y 5. The method of making radiator tubes which comprises extruding metalinto the form of a tube ironia blank having substantially parallellgrain throughout, the extrusion being longitudinal ofthe grain of theblank, and forming bales in the tube by indenting thewall of the tubetransversely of the grain.

6. The improvement in the-art of making` v tubes by cold impactextrusion out of copper, which consists in making a copperv blank withlongitudinal grain parallel to the axis of said blank and thensubjecting said blank, unheated, to the impact of an extruding plung-`erV in the direction of said axis and thereby extruding the metalthrough an annular orifice.

'7. The process of making tubes which comprises as steps forming acylindrical rod of eleetrolytic copper of substantially homogeneouscharacter and having its grain running parallel to its axis, cuttingsaid rod transversely to form a cylindrical blank,

axially indenting one end of the blank, placing the blank in the die ofan extruding press with the indented end of the blank opposed tothepress plunger, and actuating the plunger to extrude the blank in anaxial direction into a. thin Walled tube. v

. Signed by me at Lowell, Mass., this 17th day of November, 1922.

WILLIAM J. ROBINSON.

